The present invention relates to a three-way valve for switching a pipe circuit and, more particularly, to a three-way valve for switching refrigerant flow of a heat pump type refrigeration cycle.
In heat pump type air conditioners, a four-way valve is generally used for switching cooling and heating operations. The flow of refrigerant is changed by this four-way valve. However, a conventional four-way valve has a complex structure and is expensive. Further, gas leakage from a high pressure side to a low pressure side and heat leakage from a high temperature side to a low temperature side cannot be prevented. For example, heat loss is about 150 kcal/hour, degrading the performance.
Recently, a three-way valve 10 as shown in FIGS. 1 and 2 has been proposed for the heat pump type refrigeration cycle. The three-way valve 10 has left and right chambers 16 and 18 and a central chamber 20 which are partitioned by two partition walls 12, 14. First and second communicating holes 22 and 24 are formed in the partition walls 12 and 14, respectively. A connecting rod 26 is slidably extended through the first and second communicating holes 22 and 24. Needle valves 28 and 30 which are disposed in the left and right chambers 16 and 18 are connected to the ends of the connecting rod 26, respectively. Openings 32, 34 and 36 are formed in the chambers 16, 18 and 20, respectively. The first opening 32 which is formed in the left chamber 16 is connected to an outlet port of a compressor through a first electromagnetic valve and to an outdoor heat exchanger. The second opening 34 which is formed in the right chamber is connected to the outlet port of the compressor through a second electromagnetic valve and an indoor heat exchanger. The third opening 36 which is formed in the central chamber 20 is connected to an inlet port of the compressor.
As shown in FIG. 1, when the needle valve 28 closes the first communicating hole 22, the needle valve 30 opens the second communicating hole 24. When the needle valve 30 closes the second communicating hole 24, the needle valve 28 opens the first communicating hole 22, as shown in FIG. 2.
When the first electromagnetic valve is opened and the second electromagnetic valve is closed, the refrigerant flows through the right chamber 18 and central chamber 20 as shown in FIG. 1. Then, when the first electromagnetic valve is closed and the second electromagnetic valve is opened, the refrigerant with high pressure in the left chamber 16 flows through the outdoor heat exchanger and indoor heat exchanger, and the right chamber 18 and central chamber 20. Therefore, the pressure of the refrigerant in the left chamber 16 is reduced to be lower than that of the refrigerant in the right chamber 18. So, the needle valve 30 is moved to narrow the second communicating hole 24 by the pressure difference. That is to say, the needle valve 28 is moved to open the first communicating hole 22. Furthermore, the needle valve 30 is moved to close the second communicating hole 24 by the fast flow of the refrigerant passing through the narrowing gap between the needle valve 30 and the second communicating hole 24. Therefore, as shown in FIG. 2, the second communicating hole 24 is closed. At this moment, the other needle valve 28 opens the first communicating hole 22. The refrigerant flows in a loop composed of the compressor, the second electromagnetic valve, the indoor heat exchanger, a capillary tube, the outdoor heat exchanger, the left chamber 16, the central chamber 20 and then the compressor.
When the other needle valve 30 closes the second communicating hole 24, the needle valve 28 and the first communicating hole 22 preferably have only little clearance. Because, when the first electromagnetic valve is released, the movement of the needle valve 28 must be minimized so that leakage of the refrigerant through the clearance is also minimized. It is noted that the needle valve 28 and the other needle valve 30 are connected through the rigid connecting rod 26. When the needle valve 28 is biased by the differential pressure and the first communicating hole 22 is sealed, the other needle valve 30 and the second communicating hole 24 are slightly separated. The refrigerant passing through this clearance has a pressure loss. This pressure loss results in significant lessening of heating/cooling performance.
When the clearance between the other needle valve 30 and the second communicating hole 24 is made wide, the gap between the needle valve 28 and the first communicating hole 22 becomes wide accordingly. This may cause an increase in leakage of the refrigerant, as described above, entailing undesirable results. In this manner, the three-way valves which have been hitherto proposed have simple construction but do not solve the above problems.